Question

Consider a 10Mbps Ethernet network consisting of 20 nodes interconnected by a bus topology with a single bridge placed in the approximate center of the network resulting in an equal umber of nodes on each side of the bridge.

1. Briefly explain why collisions can/cannot occur.

2. If two pairs of nodes attempted to communicate at the same time, discuss the throughput they can achieve.

Answer 1

a) Collisions

Ethernet networking the utilizing bus topology in 10Mbps Ethernet comprising of 20 hubs utilizes coaxial links for interconnecting to the hubs.

• can happen:

collision can also happen when at least two hubs in an organization endeavor to communicate information over an organization simultaneously and also will free the information and not finish the transmission.

• cannot happen:

CSMA/CD is an organization protocol in which the transporter transmission in the medium access control layer and also it is utilized in Ethernet topology to evade the impacts in the networks.

In this way the hubs must recognize if they would be communicating at same time as another hub and thus they could stop and try again when first hub transmission finishes then another hub will be sending the information and hence the collision in the network will not happen thereby saving the loss of data

b)

Throughput

Throughput quantifies the number of packets shown up at their destinations effectively

N= number of nodes

B= bandwidth

• In Pure aloha :

Throughput=Efficiency*Bandwidth

=(N*e^-2N)*B

=(20*e^-40)10*10^6

Throughput =8.4967085*10^-10

• In slotted aloha :

Throughput=Efficiency*Bandwidth

=(N*e^-N)*B

=(20*e^-20)10*10^6

Throughput =0.41223072448

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